Servo drive repair leads to electrical fire

[roadking]

What a mess. Four weeks ago, my Fanuc 0mc equipped VMC displayed an alarm 434, low voltage to the Z axis servo drive. The machine is powered by an American Rotary phase converter. Since the installation, my phase to phase voltage had been 241, 228, 232. Fanuc suggested that the incoming power supply was to high and dirty, so I installed a buck / boost transformer and had Will at American Rotary help me custom balance the phase converter. My new voltage was 226, 226, 227. The 434 alarm remained.

After six telephone calls in three weeks with Fanuc, I made no progress. I even sent them the top board, and it checked out fine. I had them send a tech out to me last Friday, and he replaced a "Q 1" module while he had the unit disassembled. My machine appeared to work just fine. I have run the machine twice since the repair ( 1.6 hours over 6 days).

Yesterday, after start-up I homed X and Y axis, then Z. After I commanded Z to program zero, I heard the phase converter load up and make low pitch humming sounds. I heard popping noises from the control cabinet of the machine, and I quickly powered down. The cabinet was full of smoke, and the wires on the bottom left of the Z axis servo drive unit were burnt. One of them was disconnected, possibly burned off. The phase converter has no damage.

Today I will take some pictures of this mess for my records, and Fanuc is scheduled to come out on Monday. My questions are these:

1. What did I do that allowed this to happen?
2. What did I overlook that allow this to happen?
3. Did Fanuc inadvertently cause this electrical fire because of the repair?
4. Do I have options other than getting Fanuc to come to my machine?
5. What other questions should I be asking?

This is my only CNC machine, and I am a one man operation. Machining is a part-time job for me, that I get to do after my full time job as a millwright. I am willing to invest my time and money to repair this machine, however I am handicapped because I know so little about controllers and electronics in general. I sure could use some help.

[ben_heinman]

Many times when I've experienced this alarm it has been a loose wire or connection somewhere. I suggest turning off the power opening your electrical cabinet and checking all your connections (loose wires and spots where 2 wires are connected at one point). I would concentrate on your power to and from the contactors and overloads as wells as the cables to the drives and amps.